1. Field of the Invention
The present invention relates to a method and device for applying equal tension on two or more tendons as they are being attached to a tibia in knee reconstruction surgery.
2. Description of Related Art
The Anterior Cruciate Ligament (ACL) is a short (2.5-5.0 cm) stout ligament in the center of the knee. This ligament generally attaches on the femur in the postero-lateral aspect of the inter-condylar notch. The other end of the ACL attaches to the tibia in the center of the tibial plateau just anterior to the Posterior cruciate ligament (PCL) attachment. The main function of the ACL is to resist anterior translation of the tibia in reference to the femur.
When this ligament is torn, the knee loses some of its stability and this can lead to symptoms such as giving way, effusions and pain. Also other structures in the knee are at risk for damage with a torn ACL such as the menisci and cartilage surfaces.
Because of these problems, if a person suffers an injury resulting in a tear of the ACL, it is frequently recommended to reconstruct this ligament, as it has no ability to heal itself.
ACL reconstruction attempts to replace the torn or insufficient ACL with tissue (graft) that will replicate its function as much as possible.
In ACL reconstruction there are three main issues, which need to be addressed:    1) Strong fixation of the graft on the femoral side and an intra-articular exit point (femoral side) that mirrors the attachment of the native ACL.    2) Strong center (intra-articular) portion of the graft, which mimics or surpasses the strength and other properties (e.g. stiffness, flexibility, tension) of the native ACL.    3) Strong fixation of the graft on the tibial side and an intra-articular exit point (tibial side) that mirrors the attachment of the native ACL.
A common graft used in ACL reconstruction is the harvested tendons of both the Semitendinosus and Gracilis hamstring muscles. These tendons are commonly doubled over in most surgeries making a graft complex, which has 4 strands. This 4-strand complex surpasses the strength and stiffness of most native ACLs. These properties are best realized when the tension in each of the 4 strands is equal.
In order to address issues 1 and 3 from above, tunnels are commonly drilled into both the femur and tibia. The tunnels allow for strong fixation (and biologic attachment) of the graft within them and the intra-articular exits of the tunnels reflect the attachment sites of the native ACL.
In general the tibial tunnel is drilled first and then the femoral tunnel is drilled. Fixation within the tunnels usually is accomplished first on the femoral side. The most common method entails a transfixing pin or post that crosses the tunnel at a 90° angle. The tendons go around this pin (which is fixed in the bone) and this doubles the tendons while also providing fixation on the femoral side.
Starting at the transfixing pin (in the femoral tunnel) the 4 strands of the tendons go through the remainder of the femoral tunnel, and then exit into the joint, traverse the joint, then go into the tibial tunnel and finally exit anteriorly out of the tibia.
Fixation on the tibial side is commonly achieved with the use of spiked washers and screws, staples, or other specialized screws.
Prior to the fixation on the tibial side, the tendons are placed under tension by pulling on the sutures that are attached to the ends of the tendons. While pulling on the tendons the fixation device is applied on the tibial side. This completes the procedure.
Examples of non-analogous devices used in knee reconstruction procedures are disclosed in the following non-analogous U.S. patents.
U.S. Pat. No.PATENTEE5,628,756Barker et al.5,646,266Li6,036,694Goble et al.6,056,752Roger6,214,007Anderson6,152,928Wenstrom, Jr.6,235,057Roger et al.6,290,711Caspari et al.